The quiet of a hospital in the Philadelphia-area suburbs was broken yesterday when an armed mental patient killed a caseworker and got into a gunfight with his armed psychiatrist.

Authorities say the afternoon incident at Mercy Fitzgerald Hospital's wellness center might have been worse, if not for quick action on the part of the pistol-packing doctor and several of his unarmed colleagues:

Delaware County District Attorney Jack Whelan said a mentally troubled Richard Plotts walked into the Psychiatric Unit on the third floor of the building with his caseworker, 53-year-old Theresa Hunt of Philadelphia.

Plotts and Hunt went into Dr. Lee Silverman's office, and an argument erupted.

Hunt shut the door and called police. Seconds later there was gunfire. When it was over, Hunt was dead and Plotts and Silverman wounded.

They believe the doctor then pulled out his own gun, firing several times. Plotts was critically injured, hit twice in the torso and once in the arm.

After the shooting, another doctor and caseworker reportedly burst into the office to find "Silverman holding his bloody face and Plotts still holding his weapon." They proceeded to wrestle Plotts down and take his weapon. He is currently in critical condition; Dr. Silverman was treated and released.

If he pulls through, Plotts will be charged with first degree murder for Hunt's death, authorities say. Silverman faces no charges and was praised for his action in the shootout, in which one of Plotts' bullets narrowly missed him. It was unclear how long Silverman had been armed at work or whether he'd begun carrying as a result of his experience with Potts, though the district attorney said he "did receive information that there were incidents involving Mr. Plotts and hospital personnel including the doctor's staff in the past."

Also unclear was why Plotts had the means to fatally shoot his caseworker in the first place. Upper Darby Police Superintendent Michael Chitwood told a local paper that Plotts had been committed for psychiatric evaluation in that town "on at least three occasions" and had been banned from at least one facility for his aggression.